A controller is generally a device used to control other processes or external devices. A microcontroller is an electronic device, a highly integrated chip, which performs controlling functions. A microcontroller includes all or most of the parts needed for implementing a controller but physically, is a smaller device (e.g., and integrated circuit). The demands for reduction in the size of microcontrollers, due to the nature of their use, have led to the miniaturization of the electronic components constituting a microcontroller. The reduction in the physical size of microcontrollers has caused an increase in the scope of their use across different fields. The spectrum of the application of microcontrollers varies across different and diverse disciplines. For example, microcontrollers are being used in the field of medicine, for example a pacemaker monitoring a patient's heart beats, or in the field of meteorology, where a microcontroller is installed in a very remote location to periodically record, log and report atmospheric conditions. In many instances more than one microcontroller is found in a single device to perform a certain function. In today's technology, almost all electrical and electromechanical devices use microcontrollers for the purpose of controlling or monitoring different processes.
Microcontrollers require a source of power for their operation. Most microcontrollers only support 4.5 to 5 volts operations and thus require a power source capable of supplying that amount of power. Dry cell batteries are typically used to support a microcontroller's power demand. To meet such power requirements, generally 2-3 dry cells (e.g., type AAA) power the microcontrollers. Comparing the size of electronic components used in a typical microcontroller and the batteries used to power the device, the batteries are the most voluminous component in a microcontroller. With the ever increasing demand for reduction in the size of microcontrollers, a need exist to reduce the size of the power supply providing power to the microcontrollers.
Effort should be made to conserve energy during all modes of operation. A typical microcontroller does not operate on a continuous basis, the device is generally programmed to operate based on the demand or in accordance with a programmed schedule. Once the microcontroller performs its function it either goes to an idle mode or to a sleep mode until it is summoned to perform another function. It is during the performance of a function, during operational mode, that a microcontroller requires more power to meet its operating voltage requirements. A microcontroller has a much lower power requirement during its idle or sleep mode than when it is performing a function. For example, a microcontroller which is installed in a remote location to measure environmental data at some-regular interval need not be in its operational mode at all times. The microcontroller may be in its sleep mode most of the time, except when it has to take the environmental data measurements. When measurements are required, the microcontroller wakes up, takes the measurements, logs the data and then goes to sleep. A microcontroller may be placed in a halt mode, where all activities are ceased and it has no power requirements. The only way to wake up the device is by reset or by device interrupt. For example, in a laptop keyboard, where power saving is required, the microcontroller is in halt mode until it detects a keystroke. When the microcontroller detects a keystroke, it wakes up, its mode changes from sleep mode to operation mode. Therefore an efficient method is needed to supply a microcontroller with power on demand and conserve power when the microcontroller is in sleep or idle mode.
Board space on a typical Printed Circuit Board (PCB) is limited, thus efforts should be made to optimize foot prints of the devices used and the number of pins for inter connection. The present generation of microcontrollers, requiring operating voltage of 4.5-5 volts, uses fewer battery cells than prior generations in order to perform the same or a similar function. To supply the operating voltage requirements with a smaller number of dry cells, a separate power supply pump circuit is used to boost the relatively lower supplied voltage value to the required operating voltage value. A separate power supply pump circuit meets the demand of a microcontroller as far as the operating voltage is concerned, but such a power supply pump circuit has its own disadvantages. A separate power supply pump circuit requires additional space on the printed circuit board (PCB) and additional pins for interconnections. Space on the PCB for any device and pin connections are scarce commodities and efforts are always made to optimize such requirements. Minimizing the space requirements and reducing the number of pins for the interconnection of devices are needs to be addressed by designers and manufacturers.
To efficiently conserve power, a continuous interaction between a microcontroller and its power supply pump circuit is necessary. Such an interaction includes the microcontroller informing the power supply pump circuit of its power demands and the power supply pump circuit supplying the required power when the power is needed. Conventional power supply pump circuits communicate with microcontroller and supply power to the microprocessor based on the microprocessor's power demand. However, the very process of communicating (e.g., driving input and output pins) decreases the efficiency of power conservation. Optimal operation of a microcontroller requires efficient communication between the power supply pump circuits and the microcontrollers.